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Multiple generations of grain aggregation in different environments preceded solar system body formation.

ABSTRACT: The solar system formed from interstellar dust and gas in a molecular cloud. Astronomical observations show that typical interstellar dust consists of amorphous (a-) silicate and organic carbon. Bona fide physical samples for laboratory studies would yield unprecedented insight about solar system formation, but they were largely destroyed. The most likely repositories of surviving presolar dust are the least altered extraterrestrial materials, interplanetary dust particles (IDPs) with probable cometary origins. Cometary IDPs contain abundant submicron a-silicate grains called GEMS (glass with embedded metal and sulfides), believed to be carbon-free. Some have detectable isotopically anomalous a-silicate components from other stars, proving they are preserved dust inherited from the interstellar medium. However, it is debated whether the majority of GEMS predate the solar system or formed in the solar nebula by condensation of high-temperature (>1,300 K) gas. Here, we map IDP compositions with single nanometer-scale resolution and find that GEMS contain organic carbon. Mapping reveals two generations of grain aggregation, the key process in growth from dust grains to planetesimals, mediated by carbon. GEMS grains, some with a-silicate subgrains mantled by organic carbon, comprise the earliest generation of aggregates. These aggregates (and other grains) are encapsulated in lower-density organic carbon matrix, indicating a second generation of aggregation. Since this organic carbon thermally decomposes above ?450 K, GEMS cannot have accreted in the hot solar nebula, and formed, instead, in the cold presolar molecular cloud and/or outer protoplanetary disk. We suggest that GEMS are consistent with surviving interstellar dust, condensed in situ, and cycled through multiple molecular clouds.

SUBMITTER: Ishii HA

PROVIDER: S-EPMC6042113 | biostudies-literature | 2018 Jun

REPOSITORIES: biostudies-literature

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Multiple generations of grain aggregation in different environments preceded solar system body formation.

Ishii Hope A HA Bradley John P JP Bechtel Hans A HA Brownlee Donald E DE Bustillo Karen C KC Ciston James J Cuzzi Jeffrey N JN Floss Christine C Joswiak David J DJ

Proceedings of the National Academy of Sciences of the United States of America 20180611 26

The solar system formed from interstellar dust and gas in a molecular cloud. Astronomical observations show that typical interstellar dust consists of amorphous (<i>a</i>-) silicate and organic carbon. Bona fide physical samples for laboratory studies would yield unprecedented insight about solar system formation, but they were largely destroyed. The most likely repositories of surviving presolar dust are the least altered extraterrestrial materials, interplanetary dust particles (IDPs) with pro ...[more]

PMID: 29891720

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Project description:BackgroundAlthough the relationship between residential food environments and health outcomes have been extensively studied, the relationship between body mass index (BMI) and multiple food environments have not been fully explored. We examined the relationship between characteristics of three distinct food environments and BMI among elementary school employees in the metropolitan area of New Orleans, LA. We assessed the food environments around the residential and worksite neighborhoods and the commuting corridors.Research methodology/principal findingsThis study combined data from three different sources: individual and worksite data (ACTION), food retailer database (Dunn and Bradstreet), and the U.S. Census TIGER/Line Files. Spatial and hierarchical analyses were performed to explore the impact of predictors at the individual and environmental levels on BMI. When the three food environments were combined, the number of supermarkets and the number of grocery stores at residential food environment had a significant association with BMI (β = 0.56 and β = 0.24, p < 0.01), whereas the number of full-service restaurants showed an inverse relationship with BMI (β = -0.15, p < 0.001). For the commute corridor food environment, it was found that each additional fast-food restaurant in a vicinity of one kilometer traveled contributed to a higher BMI (β = 0.80, p <0.05), while adjusting for other factors. No statistical associations were found between BMI and worksite food environment.ConclusionsThe current study was the first to examine the relationship between BMI and food environments around residential neighborhoods, work neighborhoods, and the commuting corridor. Significant results were found between BMI and the availability of food stores around residential neighborhoods and the commuting corridor, adjusted for individual-level factors. This study expands the analysis beyond residential neighborhoods, illustrating the importance of multiple environmental factors in relation to BMI.

Project description:The inherent intermittency of solar power due to diurnal and seasonal cycles has usually resulted in the need for alternative generation sources thereby increasing system operation costs. However, when solar power is spread over a large geographical area with significant time differences, the intermittency can be significantly reduced and also the electricity market balancing cost. The aim of this article is to address the fundamental scientific question on how the intermittency of solar power generation is affected by aggregation, which is of great interest in the wider power and energy community and would have profound impacts on the solar energy integration into the energy supply and Net-Zero Implementation. This article goes beyond the typical regional analysis by investigating solar power intermittency at 5 aggregation levels from a global perspective based on global 7 year hourly meteorological re-analysis data with a fine spatial resolution of [Formula: see text]. In the proposed assessment framework, a coefficient of variation (CV) is used to quantify solar power intermittency and hence characterize the potential benefits of wide area solar power aggregation. A duration curve is used to characterize the intermittency in terms of power availability and a probability density function is further employed to investigate the dispersion and scaling behavior of CV at different aggregation levels. The findings indicate that the CV of solar power generation of 'Inner Mongolia' in China drops from 129.65 to 105.65% in the level of 'Asia' (by 24% decrease), to 56.11% in 'Asia-North_America' (by 73.54% decrease) and to the smallest 43.50% in 'Global' (by 86.15% decrease), nearly 3.5 times of that in 'Asia'; (b) the availability of solar power generation increases from 52.17% in Germany, to 73.30% in 'Europe_EU_plus', to 77.82% in 'Europe', to 98.59% in 'Europe-North_America' (80.60% in 'Europe-Africa', 96.90% in 'Europe-Asia'), to 100% in 'Global'. Finally, conclusions and recommendations are provided to support a Net-Zero strategy.

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Multiple generations of grain aggregation in different environments preceded solar system body formation.

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Multiple generations of grain aggregation in different environments preceded solar system body formation.

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